The present invention relates generally to retail transaction systems and, in particular, to a radio frequency identification (RFID) system with separately located transmitters and receivers.
RFID technology provides an alternative to bar code reader technology for distinguishing and recording items for purchase. RFID may result in labor savings to retailers, since it may obsolete conventional methods of identifying products.
Some of the uses of RFID technology are disclosed in U.S. Pat. No. 6,019,394 assigned to the assignee of the present invention. This patent is hereby incorporated by reference.
RFID tags may be permanently attached to products. RFID tags permanently attached to clothing and other items may be worn or carried by customers into stores. These RFID tags may be detected by RFID interrogators within the stores.
RFID systems that are currently being developed include an integrated unit containing uplink and downlink circuitry. The uplink and downlink circuitry sends a downlink transmission signal with sufficient energy to stimulate RFID tags, and receives an uplink signal containing responses from the tags.
Since the uplink signal is of significantly less energy than the downlink signal, the integrated unit must be placed close enough to the RFID tags to be able to receive the uplink signal. In a store with multiple intergrated units, placement of integrated units close enough to the RFID tags causes a redundancy in downlink signals and an excess of radio frequency (RF) energy.
It would be desirable to provide an RFID system with separately located transmitters and receivers.